A tool of this nature is known from DE 202 10 453 U1 (Cooper), wherein the working volume within the hydraulic impact mechanism is connected to an additional volume within the hydraulic cylinder through a small hole, which is closed during the pulse by a plate. A cover sealed with O-ring seals closes the hydraulic cylinder and thus defines the complete working volume of the pulse unit, because it is not adjustable for the setting of different working volumes. A spacer ring presses the cover against the cylinder wall and a locking ring permanently fixes the cover. Due to the defined mounting position of the locking ring, the distance between the hydraulic cylinder and the cover and thus also the working volume is defined and cannot be changed. The space for the working fluid cannot be adjusted and the required amount of the working fluid can only be provided by the addition or removal via a filling opening. Conventionally, the chamber is first completely filled with working fluid and then the removal occurs with syringes, which draw the fluid out of the inner space until a desired volume is obtained. This filling procedure is very cost-intensive and imprecise. Furthermore, it is not possible to change the working volume.
From the document DE 40 18 084 C1 a pulse nutsetter is known, the hydraulic impact mechanism of which is closed off on one side with a hydraulic impact mechanism cover, which is fixed, secured against turning, by means of a positioning pin. A cover plate then closes off the complete assembly. In this hydraulic impact mechanism the working volume remains constant.
From DE 698 07 013 T2 a tool is known, which has an impact wrench with a motor which rotates a drive element within a fluid chamber, wherein the drive element is fitted with a common fluid chamber with a variable volume. With an expansion of the hydraulic fluid the common chamber accepts the additional fluid volume. With the decrease in the expansion the common chamber passes the fluid back into the fluid chamber. The compensation is handled by an elastically deformable membrane which consists of two areas. The first area is connected to the fluid chamber via a channel and the second membrane layer is intended to provide protection against destruction due to the chemically aggressive hydraulic fluid. The increase in volume within the common fluid chamber leads to a deformation of the membrane and thus to enlargement of the working volume. When the temperature of the hydraulic fluid decreases, the excess fluid, which previously passed into the common chamber, returns via the channel into the common chamber and the membrane is relieved. The working volume can thus only be changed depending on the pressure of the working fluid. A specific volume setting is not possible.
Accordingly, the object of the invention is to improve a tool of the type mentioned in the introduction such that the working volume can be set within the hydraulic impact mechanism irrespective of the consistency of the working fluid and at any time.